1. Field of the Invention
The present invention generally relates to a continuous process for forming parts by precision microfabrication and, more particularly, to a process for fabricating inkjet orifice plates for printheads of inkjet printers.
2. State of the Art
It is known to provide printheads for inkjet printers wherein the printheads each include a substrate, an intermediate barrier layer, and a nozzle plate including an array of nozzle orifices, each of which is paired with a vaporization chamber in the substrate. Also, a complete inkjet printhead includes mean that connect the vaporization cavities to a single ink supply reservoir.
In practice, the print quality of an inkjet printers depends upon the physical characteristics of the nozzles in its printhead. The geometry of a printhead orifice nozzle affects, for instance, the size, trajectory, and speed of ink drop ejection. In addition, the geometry of a printhead orifice nozzle affects the ink supply flow to the associated vaporization chamber and, in some instances, can affect the manner in which ink is ejected from adjacent nozzles.
In practice, nozzle plates for inkjet printheads often are fabricated from nickel in an lithographic electroforming processes. One example of a suitable lithographic electroforming process is described in U.S. Pat. No. 4,773,971, assigned to the Hewlett-Packard Company of Palo Alto, Calif. In the process described in the patent, nickel nozzle plates are formed with a reusable mandrel that includes a conductive material covered with a patterned dielectric layer. To form a nozzle plate, the reusable mandrel is inserted in an electroforming bath so that nickel is electroplated onto the conductive areas of the mandrel.
An article entitled "The ThinkJet Orifice Plate: A Part With Many Functions" by Gary L. Siewell et al. in the Hewlett-Packard Journal, May 1985, pages 33-37, discloses an orifice plate made by a single electroforming step wherein nozzles are formed around pillars of photoresist with carefully controlled overplating. More particularly, the article discloses that a stainless steel mandrel is: (1) deburred, burnished, and cleaned; (2) a layer of photoresist is spun on the surface and patterned to form protected areas for manifolds; (3) the exposed surface is uniformly etched to a specified depth; (4) the resist is removed and the mandrel is burnished and cleaned again; (5) a new coat of photoresist is spun on and patterned to define the barriers and standoffs; and (6) the barriers and standoffs are etched.
Further, the Siewell art discloses that the orifice plate can be made by: (1) laminating the stainless steel mandrel with dry film photoresist; (2) exposing and developing the resist so that circular pads, or pillars, are left for orifices or nozzles; (3) electroplating the mandrel with nickel on the exposed stainless steel areas including the insides of grooves etched into the mandrel to define the barrier walls and standoffs; (4) peeling the plating from the mandrel, the electroplated film being easily removed due to an oxide surface on the stainless steel which causes plated metals to only weakly adhere to the oxide surface; and (5) stripping the photoresist from the nickel foil. According to the article, the nickel foil has openings wherever the resist was on the mandrel. Still further, the article states that the resist is used to define edges of each orifice plate, including break tabs which allows a large number of orifice plates formed on the mandrel to be removed in a single piece, bonded to a mating array of thin-film substrates and separated into individual printheads.